use this instead of class valuables for thread safe.

thread_value_store.rb

# -*- encoding : utf-8 -*-

#
# for thread safe
#
class ThreadValueStore
  @@value_store = {}
  @@store_types = {}

  def self.reserve(name, store_type = :value)
    pid = rand.to_s
    set_store_type(name, store_type)
    @@value_store[name] ||= {}
    if type_of_store_by_name(name) == :array
      @@value_store[name][pid] = []
    else
      @@value_store[name][pid] = nil
    end

    pid
  end

  def self.set(name, pid, value)
    if type_of_store_by_name(name) == :array
      @@value_store[name][pid] << value
    else
      @@value_store[name][pid] = value
    end
  end
  class << self
    alias_method :push, :set
  end

  def self.unshift(name, pid, value)
    @@value_store[name][pid].unshift(value)
  end

  def self.get(name, pid)
    @@value_store[name][pid]
  end

  def self.release(name, pid)
    @@value_store[name].delete(pid)
  end

  private 
  def self.type_of_store_by_name(name)
    @@store_types[name]
  end

  # @param name [Symbol]
  # @param store_type [Symbol] :array and else
  def self.set_store_type(name, store_type)
    @@store_types[name] = store_type
  end
end